The present invention relates communications networks, and more particularly to digital communications networks. Even more particularly, the present invention relates to extension interface units of fixed-wireless networks including point to multipoint radio communications sites.
Point to multipoint radio communication networks are generally known in the art. A competitive local exchange carrier uses the point to multipoint system to provide services to subscribers within remote geographic regions from backhaul facilities. Generally, the point to multipoint system comprises a hub site containing several hub terminals, a plurality of remote terminals, and a central office. The central office manages the system and is coupled to each hub terminal of the hub site via a backhaul infrastructure, such as a fiber network built throughout a city. The central office is coupled to several other networks; such as, Public Switched Telephone Networks (PSTN), interexchange carriers (IXC), Internet Service Providers (ISP), and other data delivery systems. Each hub terminal contains a radio system that communicates with the remote terminals at the remote subscribers within the geographic area surrounding the hub terminal. The remote terminals provide an interface to the network for the remote subscribers. Thus, the point to multipoint radio system provides its subscribers with voice, video, and data connections to other networks that are available through the backhaul facilities.
Typically, a remote terminal of a point to multipoint communications system has a limited number of interface ports wherein subscribers may interface. The subscribers interface with a subscriber interface card or interface module. The subscriber interface card interfaces with a bus system that carries traffic between the remote terminal and the subscriber interface card. Commonly, there may be more subscribers that wish to interface with the communications system than there are interface ports. A prior art solution is to provide an extension interface module, such as a bus repeater, which is placed into an interface port of the remote communications terminal.
The prior art extension interface module couples to an extension communications link, such as a ribbon cable, which extends to an extension interface unit having more interface ports. Thus, more interface ports are provided so that more subscribers can interface to the remote terminal. However, disadvantageously, the bus repeater and the ribbon cable can only extend the bus system a few feet. Thus, subscribers at different locations within the subscribers"" premises have to provide additional wireline connections to the extension interface unit, since it is typically located in one location with the subscribers"" premises.
Furthermore, in a typical prior art point to multipoint system, most of the current backhaul infrastructure supports time division multiplexed (TDM) or xe2x80x9csynchronousxe2x80x9d modes of transportation. Most voice communications use TDM. A relatively new technology, asynchronous transfer mode (ATM), is gaining popularity as a high speed, packet switched architecture that integrates voice, data, video, and multimedia. ATM outperforms TDM as a high speed data carrier, but the quality of service of voice is less known than TDM. ATM is desirable for large companies, universities, and financial institutions that have a wide variety of communications needs.
The prior art point to multipoint systems support only TDM (synchronous) or only ATM (asynchronous) transport modes. ATM networks are not as widespread as TDM networks since the infrastructure is costly and not fully in place; thus, most subscribers obtain TDM services, while a growing number obtain ATM services through separate networks. And therefore, the bus systems, bus repeaters, ribbon cables, and extension interface units carry either TDM traffic or ATM traffic, depending on how the communications system is configured. Thus, disadvantageously, if a subscriber wishes to obtain both TDM and ATM services, the subscriber must subscribe to different communications networks (TDM and ATM), each having different subscriber interface cards, different bus repeaters, different ribbon cables and different extension interface units.
The present invention advantageously addresses the needs above as well as other needs by providing an extension module and extension interface unit that extend a bus greater than just a few feet and expand the number of interfaces to the communications system. Advantageously, the extension system supports both TDM traffic and ATM traffic.
In one embodiment, the present invention can be characterized as an extender interface module for expanding a number of interface modules that may interface with a communications system includes a multi-transport mode bus interface that couples to a multi-transport bus and the multi-transport mode bus interface carries signals to and from a communications terminal. The signals comprise a plurality of transport mode signals. Also included are a signal formatter coupled to the multi-transport mode bus interface, a converter coupled to the signal formatter, wherein the converter converts the signals from a multi-transport mode bus format to a format suitable for transmission over an extension communications link, a transceiver coupled to the converter for transmitting the signals over the extension communications link, and the extension communications link coupled to the transceiver.
In another embodiment, the present invention can be characterized as an extension system for expanding the number of interface modules that interface with a communications system. The system includes a communications terminal including a first multi-transport mode bus that carries signals comprising a plurality of transport mode signals, a plurality of interface ports coupled to the first multi-transport mode bus, and a first extension interface mode coupled to one of the plurality of interface ports, wherein the first extension interface module converts the transmission format of the signals to a transmission format of an extension communications link. The system further includes the extension communications link coupled to the first extension interface module, wherein the extension communications link functions as an extension of the first multi-transport mode bus, a second extension interface module coupled to the extension communications link, an extension unit coupled to the second extension interface module containing a second multi-transport mode bus, wherein the second multi-transport mode bus carries the signals, and a plurality of expansion interface ports coupled to the second multi-transport mode bus of the extension unit.
In an additional embodiment, the present invention can be characterized as a method of extending a bus of a communications system through an extension link comprising the steps of: receiving signals from the bus, wherein the signals comprise a plurality of transport mode signals; buffering the signals; converting the signals from a bus transmission format to an extension link transmission format of an extension link; and transmitting the signals having been converted through the extension link, wherein the extension link functions as an extension of the bus.
In a further embodiment, the present invention can be characterized as a method of expanding the number of interfaces and providing an extension interface unit of a communications terminal comprising the steps of: coupling a first interface module to a first bus of the communications terminal, wherein the first bus carries signals comprising a plurality of transport mode signals, wherein the first bus carries the signals from the communications terminal to the first interface module; providing an extension communications link; coupling a first end of the extension communications link to the first interface, wherein the extension communications link carries the signals; coupling a second interface module to a second end of the extension communications link; coupling a second bus of an extension unit to the second interface module, wherein the second bus carries the signals; and coupling a plurality of expansion interface ports to the second bus of the extension unit.